1. Field of the Invention
The present invention relates to an apparatus and a method for controlling a data transmission rate in a broadband wireless communication system. More particularly, the present invention relates to an apparatus and a method for controlling a data transmission rate and wireless resource assignment in a broadband wireless communication system.
2. Description of the Related Art
In a 4th Generation (4G) communication system, which is a next generation communication system, research for providing services of various Quality of Services (QoS) having a transmission rate of about 100 Mbps to a user are in active progress. More particularly, in the current 4G communication system, research for supporting a high speed service that guarantees a Broadband Wireless Access (BWA) communication system mobility and desired QoS is in active progress. A representative 4G communication system is an Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system.
The IEEE 802.16 communication system uses an Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA) scheme for a physical channel. The OFDM/OFDMA scheme obtains optimum transmission efficiency during high speed data transmission by performing transmission while maintaining orthogonality between a plurality of subcarriers.
In an IEEE 802.16-based broadband wireless communication system, data transmission is performed on a frame basis, and each frame is divided into a region for transmitting DownLink (DL) data and a region for transmitting UpLink (UL) data. Here, the region for transmitting the UL data includes a two dimensional arrangement of a frequency axis and a time axis, and each basic assignment unit is a slot. Each slot is assigned to only one terminal existing in one sector, and a set of slots assigned to respective terminals may be defined as a burst.
Hereinafter, a method for assigning a UL resource to a terminal in the conventional broadband wireless communication system is described.
First, a base station demodulates a received signal to extract UL transmission (Tx) power information transmitted by a terminal. In addition, the base station performs scheduling to determine priority (or service flow priority) between terminals. After that, the base station determines a UL Modulation and Coding Scheme (MCS) and an available wireless resource (the number of slots) using UL Tx power information according to the determined service flow priority. In addition, the base station transmits a resource assignment message including the determined MCS and wireless resource information to the terminal. As described above, the base station determines an MCS level and a wireless resource using the UL Tx power information received from the terminal.
Generally, when a Frequency Reuse Pattern (FRP)=1, since a UL uses the same frequency band, the Tx power (i.e., Tx signal) generated from a terminal is received by an external sector as well as a serving sector. When the amount of UL interference received from an external sector is large, reception performance of a base station (sector) deteriorates.
According to the conventional art, a base station assigns a UL resource with reference only to the Tx power information of a terminal. That is, the base station assigns a UL resource without consideration of the amount of interference on the external sector. In this case, reception performance of an external sector deteriorates and relevant QoS deteriorates. Accordingly, there is a need for an apparatus and method for controlling the amount of interference. That is, there is a need for a base station to assign a UL resource with consideration of the interference on an external sector.